Arrangement in polarized relays



March 15, 1950 5, V|GREN ETAL ARRANGEMENT IN POLARIZED RELAYS 2 Sheets-Sheet 1 Filed June 8, 1956 N N o wwm 56 5 E RWNE N 0 40?? ma mm f? W0 1 CZ r a e "J H 5 2 0w Y B Much 15, 1960 s. D. VIGREN ETAL 2,923,915

ARRANGEMENT IN POLARIZED RELAYS Filed June 8, 1956 2 Sheets-Sheet 2 IN VEN TORS Ww ML United States Patent ARRANGEMENT IN POLARIZED RELAYS Sten Daniel Vigren and Rolf Albin Zander, Stockholm, and Per Harry Elias Claesson, Danderyd, Sweden Application June 8, 1956, Serial No. 590,223

Claims priority, application Sweden July 11, 1955 Claims. (Cl. 200-93) The present invention relates to an arrangement in polarized relays and has for its object to provide a relay in which the wear of the contact system of the relay is less than in hitherto known relays of this type.

The invention is foremost characterised by the fact that the armature of the relay at least in one of its operated positions withholds at least one movable contact spring so that it is not in contact with the corresponding stationary spring. Furthermore the travel. of the contactoperating part of the armature is larger than the travel of that part of the armature which moves in the magnet air gap, the travel ratio being at least two, and preferably at least four. The armature can also be balanced with respect to its pivotal axis" so that the operation of the" relay will not be affected by accelerations or retardations to which the relay may be subjected.

Due to the said travel ratio a comparatively large contact travel displacement is achieved and consequently there can be relatively large air gaps between the contacts in open condition. Hereby the operating limits and the operating times of the relay becomes more independent of contact erosion than in previously known relays. Such a travel ratio is not practicable in the case that contact closure is eliected by the movable contacts being directly operated by the armature, since in such case the speed with which the movable contact strikes against the stationary contact will be very high, since it is equal to the speed of the contact-operating portion of the armature, and therefore contact vibrations will occur. Contact vibrations can be avoided if the contacts are indirectly operated, especially if the movable contact springs have small mass and are heavily biassed. This is accomplished by using a contact material of high quality having a large modulus of elasticity and high resistance to fatigue, e.g. steel or beryllium bronze.

Since as. a rule polarized relays are designed to have a high sensitivity and speed ofoperation, the contact travel isrelatively short. Even though this invention has for its purpose to provide a larger contact separation than in prior relays, the contact movements will be relatively small, of the order 0.1 millimetre in the most sensitive relays. This means that the length and the mass of the contact springs can be reduced. Thus the free length of the movable contact springs may be as small as. a few millimetres. in-the case that the movable contact springs are made of beryllium: bronze, steel or platinunniridium (about 80% P-t and 29% lr),the free length of, thespring can be made about-7 millimetres at a width of. 3. millimetres, a thickness of 0.1 millimetre and a contact pressure of grams. Due to these small dimensions the mass will be small and the speed of operation high, and in addition the material consumption will be very small so that a relatively expansive material, cg. platinum-iridium can be used.

. The: invention will be described more iii-particular in conjunction with: the accompanying; drawings Figures 1 to 4 show an embodiment of the invention.

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Figure 5 shows another embodiment having springs of strip material.

Figures 6 to 9 show still another embodiment of the invention having contact springs of wire material.

Figures 11 and 11a show various dimensions used in an illustrative example, and Figure 12 is a diagram relating to this example.

In Figures 1 and 2 the ordinary parts of a polarized relay are shown, viz. the armature end 1 to be actuated magnetically, the pivot 2 of the armature, the armature arm 3 for actuating the contacts, the arm 3 being attached to part 1 by means of rivets 4, the bridge 5, the

core legs 6 and 7, the coil with the core 8, and the per manent magnets 9 and 10. Alternatively a single permanent magnet can be placed at the bottom side of the bridge. Hereby the length of part 1 of the armature can be made very small. The arm 3 of the armature is preferably made of sheet metal, e.g. of the aluminum alloy known in the trade as Duralumin, having a thickness of e.g. 0.2 millimetre, and has been stiffened by means of flanges as shown in Figure 1a.

The contact spring set consists of two movable side springs 15 and 16 and a central spring 14. The central spring 14 should be considerably stiller than the side springs, and at least at its upper end it should have a larger mass than the side springs. Therefore the central spring should be made of thicker material than the side springs. At its free end the central spring is provided with a contact 26 which increases the mass and also defines a distance between the side springs. The contact-operating end of the armature is provided with a stud 17 of insulating material, e.g. nylon or Perlon. The size of stud 17 is suitably adapted to the distance between the side springs. If the width of stud 17 is less than said distance, a changeover contact of the type make-before-break is obtained, whereas if the width of the stud is larger than the said distance, there will al' ways be an air gap between at least one of the side springs and the contact on the central spring. This air gap is at least equal to the difference between the width of the stud and the said distance.

The contact springs 14 to 16 can be made of either strip material or Wire material. If wire material is used, the central spring is preferably bent at angles as will be described later with reference to Figures 9 and 10.

The contact springs 14 to 16 which may be provided with soldering lugs, are preferably fastened to a plate "11 of insulating material by e.g. moulding or fitting into grooves. The said plate is preferably displ'aceably mounted on the bridge 5 and is fixed by means of two screws l2 and 13, since if the plate 11 is displaceable, the position of the contact springs can easily be adjusted with respect to the neutral central position of the armature.

In Figures 3 and 4 the construction of the contact springs 14 to 2.6 which are made of strip material, is illustrated more in detail. The contact springs are clamped between two clamping members 18 and 19 by means of screws 2b and 21. The springs are insulated from each other in any known manner. The clamping" members are also provided with two adjusting screws 22' and 23 for limiting the armature travel.

In the embodiment according to Figure 5 the insulating stud 17 on the armature has the shape of a peg, and the stationary contact spring has been divided into two springs 14a and lab.

Figures 6 to 8 show an embodiment of the invention in which wire springs are employed. In these figures the various parts are designated by the same numerals as the corresponding parts in the previous figures. The contact spring wires 14a, 14b, 15 and 16 are bent in U- shape about a tube 24 of insulating material. Furtherclamping means 18 and 19 by means of spacing washers 25 and a screw 20. Those ends of the contact spring wires which do not serve as contacts, can be used as soldering lugs. The contact spring wires 14a and 1 3:) which are comparatively immovable, are clamped against or attached to a spacing washer t io which determines the distance between them, the said distance being such that the operating stud 17 on the armature can be inserted between the side springs as previously described. The stationary contact springs 14a and 14!; are bent at angles (see Figure 9) so that the contact making portions thereof run at right angles to the movable contact springs. Alternatively the movable contact springs can be bent instead of the stationary springs, in which case the stud 17 on the armature should preferably have its main extension in a direction at right angles to the plane of the relay bridge 5.

Instead of the two stationary contact springs shown in Figures 6 to 9, a single relatively rigi spring can be used in which case the free end of the spring is bent in U-shape as shown in Figure 10.

The dimensioning of the long arm of the armature will now be illustrated by a simple example of computation. It will be assumed that the armature has dimensions indicated in Figure 11 wherein all measures are in centimetres. The length of the long arm of the armature is to be computed for a minimum operating time t. The travel A of the contact operating part is assumed to be 0.01 cm. and the operating force P=l grams. For the sake of simplicity the operating force is assumed to be constant. The long arm of the armature has the length a and is assumed to be made of Duralumin having a specific gravity of 2.3, while the short arm of the armature is made of iron having a specific gravity of 8.3.

According to the so called motion equation wherein M =the moment=100 X 0.8 gramcentimetres =the angle of travel t=the time for the angular travel I =the moment of inertia It follows v Considering the long arm or" the armature as composed of a rectangular part and a triangular part (with the base=0.05a as in Figure 11) the moment of inertia with respect to axis x can be determined in accordance with known methods of computation. Thus:

After insertion of I (with g=982) and in equation 1 one obtains 0.05aXa The example given above shows that the ratio between the travel of the contact-operating end of the armature and the travel of the end located at the magnet air gap can advantageously have the value four in order that the operating time shall be short. This ratio results in the angular travel of the armature becoming very small, whereby the air gaps between the armature and the magnet poles can be made small which in turn results in a higher sensitivity of the relay. In view of this and considering that the operating time increases rather slightly with an increase in the said ratio, it may be advantageous to increase this ratio still further. However, there is an upper limit for the said ratio principally due to the fact that the force with which the armature actuates the contacts decreases when the travel ratio is increased. In view of this the said ratio can probably not be made larger than 10.

It should be noted that in a relay having a contact arrangement according to the present invention and being of the type in which the armature remains in its side position after the energizing current has been interrupted, the operating current on repeated operations will be substantially independent of contact deformation caused e.g. by contact erosion. This is of course an advantage in relays which are to operate for a predetermined current strength (limit relays).

The embodiments described above and shown on the drawings are given by way of example only, and can be varied and modified in many ways within the scope of the invention. The invention can of course also be applied to polarized relays in which the armature is provided with restoring means for restoring it to a neutral position after the energizing current has been interrupted.

What we claim is:

1. A polarized relay comprising an electromagnet, an armature of rigid magnetic material mounted for movement about a pivot axis, fixed means for producing a permanent magnetic flux in the armature, and contact means, said armature being balanced with respect to its pivotal axis and arranged to assume either of two dis tinct positions and having one end located adjacent to poles of the electromagnet and its other end located adjacent to said contact means, said contact means comprising at least two movable contact springs which are biased to engage stationary contacts when in non-operated position, said other end of the armature having contact actuating means associated therewith for keeping either of the movable contact springs out of engagement with the mating stationary contact when the armature is in either of said two distinct positions.

2. A polarized relay comprising an electromagnet, an armature, means for producing a permanent magnetic flux in the armature, and contact means, said armature consisting of a two-armed lever having one arm longer than the other and being balanced with respect to its pivotal axis, the shorter arm of the armature being positioned adjacent to poles of said electromagnet, said longer arm consisting of a strip of sheet metal, the cross section of said strip having its largest extension in a plane at right angles to the pivotal axis of the armature, said contact means comprising at least two movable contact springs which are biased to engage stationary contacts when in non-operated position, said armature being arranged to assume either of two distinct positions, and the longer arm of the armature having associated therewith means for keeping either of the movable contact springs out of engagement with the mating stationary contact when the armature is in either of said two distinct positions.

3. A polarized relay comprising an electromagnet, an armature, means for producing a permanent magnetic flux in the armature, and contact means, said armature being arranged to assume either of two distinct positions and having one end located adjacent to poles of the electroinagnet and its other end located adiacent to the contact means, said contact means comprising two movable contact springs positioned on either side of a third contact spring and being biased toward said third contact spring, said two movable springs having a considerably less stiffness than the third spring, and said armature having associated therewith means for keeping either of said movable springs out of engagement with the third contact spring when the armature is in either of said distinct positions.

4. A polarized relay as claimed in claim 3, in which said third contact spring has a larger swinging mass than said two movable contact springs.

5. A polarized relay comprising an electromagnet, an armature, means for producing a permanent magnetic flux in said armature, and contact means, said armature being arranged to assume either of two distinct positions and having one end located adjacent to poles of the electromagnet and its other end located adjacent to said contact means, said contact means comprising two outer contact springs and a central contact spring, said outer contact springs being biased toward the central contact spring, the central contact spring having a contact member giving to the central spring a mass larger than that of any of the outer springs and defining a. spacing between the outer springs, the armature having a contact operating end located within said spacing to keep either of the outer springs out of engagement with said contact member when the armature is in either of said distinct positions.

References Cited in the file of this patent UNITED STATES PATENTS 2,241,262 Keitel May 6, 1941 2,526,804 Carpenter Oct. 24, 1950 2,609,462 Joseph Sept. 2, 1952 2,614,188 Williams et al Oct. 14, 1952 2,755,346 Fisher July 17, 1956 2,763,740 Vazquez Sept. 18, 1956 2,769,880 Holmqvist Nov. 6, 1956 2,785,248 White ..Mar. 12, 1957 

